Updating a virtual library by adding more authors

I want to have a virtual library that duplicates the contents of my ereader. It seemed easiest to create a virtual library by specifying which authors were contained. I created the virtual library easily but now I want to update it by adding some more authors.

I can't find an easy way to do this. If I edit the existing virtual library, it is not clear how to add additional authors. I was hoping in the edit screen I could click on the Author's link at the bottom and the author list would appear with my current authors pre-selected; but alas that does not happen.

I am sure others have done the same kind of thing -- what is the correct technique?